Bentonite in drilling mud https://chemicalengineeringnob.com/2019/05/08/drilling-fluid-technology-2447-2/
Bentonite is added to fresh water mud for the following reasons:
- To increase hole cleaning capability
- To reduce water seepage
- To form thin cake filter cake of low permeability
- To promote hole stability in poorly cemented formation
- To overcome loss of circulation.
Southern bentonite: this is predominated by cation as an only exchangeable cation. It is mined in Texas, Alabama etc. it can be treated with sodium and sold s drilling clay.
Asbestos are group of naturally occurring fibrous silicate minerals. The basic constituent includes Chrysolite, hydrated magnesium silicate. This is used in drilling in USA and produce in Canada and other countries. Asbestos give adequate carrying capacity but no filtration control. The combination of equal amount of bentonite and Chrysolite asbestos in fresh water provides a good hole cleaning with filtration control.
Organic colloidal material are used in drilling fluids to reduce filtration, stabilize clay, flocculate drilled solid, increase carrying capacity and to serve as emulsifiers and lubricants. The organic polymers are useful in muds that have strong affinity for water; they develop highly swollen gel in low concentration. Organic polymers used in drilling fluids may be broadly classified according to the origin and composition; such polymers include starch derivatives and petrochemicals derivatives.
Basic drilling muds
Drilling fluids can be divided into the following:
- Dispersed water base mud
- Non dispersed water based mud
- Solid free system or brine (contain soluble salts)
- Oil mud with less 10% water by volume
- Invert oil emulsion mud
- Air drilling
- Aerated and foamed system.
Composition and properties of drilling fluid & completion fluids, HCH Darley, George R. Gray. Gulf publishing company, 1988, fifth edition pp 542-563
Drilling technology, steve Devereux, Penn Well coporation, 1999. Pp 145-146
Oil and gas well drilling fluid chemical, API bull 13F, first edition 1997
Gray G.R, chemical in drilling mud, oil gas J.1958. pp246-258.